Folia Morphol. Vol. 79, No. 4, pp. 863–866 DOI: 10.5603/FM.a2020.0015 C A S E R E P O R T Copyright © 2020 Via Medica ISSN 0015–5659 journals.viamedica.pl

Platysma muscle additionally innervated by a variant anterior branch of the great auricular nerve T. Jovanovski1, N. Umek1, A. Kansky2, E. Cvetko1

1Institute of Anatomy, Faculty of Medicine, University of Ljubljana, Slovenia 2Department of Maxillofacial and Oral Surgery, University Medical Centre, Ljubljana, Slovenia

[Received: 25 November 2019; Accepted: 16 January 2020]

Damage to the great auricular nerve, with consequent clinical deficits, is a common surgical complication in facial aesthetic and in head and neck procedures such as parotidectomy, neck dissection, rhytidectomy and platysma flap operations. Hence, a thorough knowledge of nerve anatomy, particularly its potential variations, is critical in reducing the associated operative morbidity. Accordingly, we report an unusual variation of the anterior branch of the great auricular nerve noted in an 81-year-old female cadaver. The nerve was observed to course into the subman- dibular region anterior and superficial to the internal jugular vein, communicating with the cervical branch of the facial nerve, while independently innervating the platysma muscle. Although several anatomical variations of the branches of the cervical plexus have been documented, our report describes unique innervation of the platysma muscle by the great auricular nerve, which provides a new insight on the motor component of the nerve. (Folia Morphol 2020; 79, 4: 863–866)

Key words: anatomic variation, great auricular nerve, rhytidectomy, parotidectomy, platysma muscle

INTRODUCTION and terminating in the postauricular area to give sen- The great auricular nerve arises from the ven- sation to the posterioinferior aspect of the auricle [8]. tral rami of the second and the third cervical spinal Clinically, injury to the great auricular nerve is a com- nerves, to fuse into its main trunk before emerging mon complication in surgical procedures in face, from the posterior border of the sternocleidomastoid head and neck, notably rhytidectomy, parotidectomy muscle at the junction of its upper and middle third, and platysma flap surgery, occurring at a rate of 6% where it resides in its most superficial location — the to 7% during rhytidectomy [2, 7, 8]. Iatrogenic or great auricular point [1, 3]. It courses superiorly and inevitable amputation of the nerve during such pro- anteriorly, and divides into the anterior and pos- cedures could incur significant complications such terior branches. The anterior branch continues in as dysesthesia or allodynia in the involved skin area, a plane between the sternocleidomastoid muscle and otalgia, discomfort on cold exposure, and traumatic the parotid gland prior to its terminal arborisation, neuroma [11]. To minimise the risk of injury to the providing sensation to the skin overlying the parotid great auricular nerve during head and neck surgical gland and anteroinferior aspect of the auricle [8]. The procedures, it is important to fully appreciate the po- posterior branch courses on the surface of the sterno- tential variations in its anatomical disposition. In the cleidomastoid muscle before reaching the mastoid area present report, we describe an anatomic variation of

Address for correspondence: Dr. N. Umek, Institute of Anatomy, Faculty of Medicine, University of Ljubljana, Korytkova 2, 1000 Ljubljana, Slovenia, tel: 00386 1 543 7314, e-mail: [email protected]

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Figure 1. Dissection of the left side of the neck showing the anterior branch of the great auricular nerve innervating the platysma muscle; A. Superficial dissection; B. Magnified view with the platysma muscle reflected; GAN ant — great auricular nerve, anterior branch; GAN post — great auricular nerve, posterior branch; COM — communicating branch; Par — parotid gland; SCM — sternocleidomastoid muscle; LON — lesser occipital nerve; FN — facial nerve; FN mand — mandibular branch of facial nerve; FN cerv — cervical branch of facial nerve; Pla — platysma muscle; FV — facial vein; RMV — retromandibular vein; IJV — internal jugular vein; SSG — submandibular salivary gland. the nerve observed during a cadaver dissection — an giving two superficial (fascial) and one deep (lobular) anterior branch of the great auricular nerve coursing branch providing sensory innervation to the skin over- into the submandibular region and supplying the lying the parotid gland and inferior part of the auricle. platysma muscle, additional to the cervical branches The anterior branch ascended obliquely over the of the facial nerve. sternocleidomastoid muscle and turned anteriorly inferior to the apex of the parotid gland, crossing CASE REPORT the retromandibular and the internal jugular veins. During the dissection of the left side of the neck In the submandibular region the anterior branch of of an 81-year-old female formaldehyde-embalmed the great auricular nerve entered the deep surface of cadaver, an unusual course of the anterior branch of the platysma muscle. The cervical branch of the facial the great auricular nerve was observed to supply the nerve divided just inferior to the apex of the parotid platysma muscle, in addition to the cervical branch- gland into the thinner anterior and thicker posterior es of the facial nerve (Fig. 1A). The dissection was branches, entering separately into the deep surface performed with the aid of the magnifying lens (4×). of the platysma muscle. A short communication con- There were no signs of previous trauma or surgical nected the thicker cervical branch of the facial nerve scars on the face and neck. The parotid fascia and the and the anterior branch of the great auricular nerve superficial cervical layer were exposed by dissection (Fig. 1B). of the whole dermal layer from the neck and face. On the right side, the great auricular nerve coursed The great auricular nerve was observed arising over the mid-body of the sternocleidomastoid mus- from and winding around the posterior border of cle posterior to the external jugular vein as a single the sternocleidomastoid muscle, coursing 1 cm supe- branch and distributed to the skin over the parotid riorly before dividing into the anterior and posterior gland. branches. Both branches then ascended beneath the platysma muscle on the surface of the sternocleido- DISCUSSION mastoid muscle. The thicker posterior branch trifur- The present report describes a cadaveric finding of cated at the posterior lobe of the parotid gland by an unusual anatomic variation of the anterior branch

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of the great auricular nerve supplying the platysma salivary duct and blood vessels that suggested a pos- muscle additional to the cervical branch of the facial sible role in the secretory mechanisms of the parotid nerve, with communication between both nerves. salivary gland [12]. In addition, it has been proposed The communications between the cervical plexus that the great auricular nerve might be involved in the and the facial nerve are well known and are reported coordination of proprioceptive information from the to originate during the seventh week of the embryon- muscle via the motor nerve which it communicates ic life [5]. Gasser [6] reported that early in embryonic with [11]. Previous reports have consistently shown life (7th week), the peripheral part of the facial nerve that the great auricular nerve variants communicate divides into several bundles from which the most with the facial nerve by terminating in to the nerve caudal bundles communicate with nerves from the trunk [4, 5, 10, 11]. second and third cervical ganglia in a plexus located in the caudal and ventral part of the second arch. CONCLUSIONS Another bundle of the facial nerve, the future cervi- Although a distinction has been made in the cal branch, pursues a ventral course and terminates literature for the great auricular nerve not having just deep to the myoblastic lamina from which the a motor component [4], our case report showed that platysma muscle develops. The observed anatomical after communicating with the cervical branch of the variation could be a consequence of the anterior facial nerve, the anterior branch of the great auricular branch of the great auricular nerve termination deep nerve independently entered the platysma muscle, to the myoblastic lamina rather than in the ventral which suggests a motor function. part of the second arch [6]. Previous reports have already described communi- Acknowledgements cations between the great auricular nerve and several We are grateful to Ivan Blažinovič for the dis- cranial nerves. Pillay et al. [9] described a variation in section work, Stanko Kristl and Friderik Štendler for the branching pattern of the great auricular nerve, technical assistance, Nataša Pollak Kristl for the figure as well as a communication between the transverse labelling, and to Dr. Chiedozie K. Ugwoke for manu- cervical nerve and the great auricular nerve in human script proofreading. The donor of the body used in foetuses. Yang et al. [11] and Diamond et al. [5] both the study is respectfully acknowledged. We would reported an unusual variation where the posterior also like to thank the Slovenian Research Agency branch of the great auricular nerve sends a small for financial support within the framework of the nerve twig (or several small twigs) into the parotid Programme Group P3-0043. parenchyma and connects with the trunk and tem- poral branch of the facial nerve, the auriculotemporal REFERENCES nerve and the auricular branch of the vagus nerve 1. Altafulla J, Iwanaga J, Lachkar S, et al. The great auricular [5, 10, 11]. Furthermore, Brennan et al. [4] described nerve: anatomical study with application to nerve grafting procedures. World Neurosurg. 2019; 125: e403–e407, doi: a communication between the great auricular nerve 10.1016/j.wneu.2019.01.087, indexed in Pubmed: 30703599. and the marginal mandibular branch of the facial 2. 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